Bike calculator - measure frame size and geometry...

How to take the measurements

Print off this Measuring Diagram PDF. Take it out to the workshop and write on it the measurements of your bikes. Once you have done a couple it takes no time at all!

These are the measurements needed:

A - Wheelbase

B - Rear axle to fork top

C - Fork

D - Front axle offset

E - Wheel radius

F - Wheel inner radius

G - Headstock length

H - Down tube to fork top

I - Top tube to fork top

J - Steering stem

K - Chainstay

L - Bottom bracket to fork top

M - Seatstay

N - Seat join to fork top

O - Saddle Displacement

When you are viewing the 'Create a map' page, when you hover over an input field when inputting data, an orange line highlights where to take the measurement.

Plainly not all bikes consist of straight lines and all this program does is build a symbolic representation. It does not model the compression of rear suspension.

I find the best way to take the measurements is to make feint pencil marks on the frame
at the specific points where I visualise tubes meeting.

The critical measurements are :

Wheelbase

Rear axle to fork top

Fork

Front axle offset

The hardest one to take is the front axle offset. Line up a long straight object (e.g. a long ruler or spirit level) with the center of the steering axis
and measure 90° from this to the axle centre. So far all bikes I have measured have a fork offset of between 35mm and 40mm.